From 87c306061bc2ee538e4e6460c4491dcef41a7f00 Mon Sep 17 00:00:00 2001
From: metagn <metagngn@gmail.com>
Date: Tue, 19 Nov 2024 11:49:41 +0300
Subject: [PATCH] disable weird type inference for object constructors (#24455)

closes #24372, refs #20091

This was added in #20091 for some reason but doesn't actually work and
only makes error messages more obscure. So for now, it's disabled.

Can also be backported to 2.0 if necessary.

(cherry picked from commit a610f23060b8a49d8b68e8ea3a8de92b3b1a6f2e)
---
 compiler/semobjconstr.nim          | 13 ++++++++-----
 tests/errmsgs/tuninstobjconstr.nim | 11 +++++++++++
 2 files changed, 19 insertions(+), 5 deletions(-)
 create mode 100644 tests/errmsgs/tuninstobjconstr.nim

diff --git a/compiler/semobjconstr.nim b/compiler/semobjconstr.nim
index e90e0bc810..1e4bb90ebc 100644
--- a/compiler/semobjconstr.nim
+++ b/compiler/semobjconstr.nim
@@ -465,11 +465,14 @@ proc semObjConstr(c: PContext, n: PNode, flags: TExprFlags; expectedType: PType
   if t == nil:
     return localErrorNode(c, result, "object constructor needs an object type")
 
-  if t.skipTypes({tyGenericInst,
-      tyAlias, tySink, tyOwned, tyRef}).kind != tyObject and
-      expectedType != nil and expectedType.skipTypes({tyGenericInst,
-      tyAlias, tySink, tyOwned, tyRef}).kind == tyObject:
-    t = expectedType
+  when false:
+    # attempted type inference for generic object types,
+    # doesn't work since n[0] isn't set and seems underspecified
+    if t.skipTypes({tyGenericInst,
+        tyAlias, tySink, tyOwned, tyRef}).kind != tyObject and
+        expectedType != nil and expectedType.skipTypes({tyGenericInst,
+        tyAlias, tySink, tyOwned, tyRef}).kind == tyObject:
+      t = expectedType
 
   t = skipTypes(t, {tyGenericInst, tyAlias, tySink, tyOwned})
   if t.kind == tyRef:
diff --git a/tests/errmsgs/tuninstobjconstr.nim b/tests/errmsgs/tuninstobjconstr.nim
new file mode 100644
index 0000000000..5d6cac304f
--- /dev/null
+++ b/tests/errmsgs/tuninstobjconstr.nim
@@ -0,0 +1,11 @@
+# issue #24372
+
+type
+  Foo[T] = object
+    x: string
+    
+proc initFoo(): Foo[string] =
+  Foo(x: "hello") #[tt.Error
+     ^ cannot instantiate: 'Foo[T]'; the object's generic parameters cannot be inferred and must be explicitly given]#
+
+discard initFoo()